This invention relates to exercise devices and more particularly to weight-lifting devices for sport-specific muscle development.
There has been much interest given recently to sports-specific or "explosive" muscle development. For example, in football, a lineman uses his arm muscles to "explosively" drive back other players. Similarly, during running events, the athlete's leg muscles explosively press off against the track field. To help develop those muscles which specifically contribute to explosive power, several weight-lifting machines have been developed.
One such machine is shown in Lang, U.S. Pat. No. 4,750,739. The Lang machine is used for "squat" type exercises where the lifter carries a barbell behind his back at shoulder level and repetitively performs "squats" by bending and straightening both of his knees. In Lang, pneumatically-driven pistons are attached to either end of the barbell and add a supplemental load to the barbell as the lifter squats. At the bottom of the squat, the chambers in the pistons are depressurized causing abrupt removal of the supplemental load so that the lifter explodes upward in reaction. A machine operating under similar principles is found in Clark et al. U.S. Pat. No. 3,540,171. In Clark, weighted platforms are moved onto or off of respective end portions of the barbell.
In both Clark et al. and Lang, the supplemental load is added to the weighted bar while the lifter's muscles experience increased bending or lengthening (eccentric contraction) and then the load is suddenly removed just before the lifter's muscles experience increased straightening or shortening (concentric contraction). Such differential loading as depending on muscle activity has been found beneficial in developing sports-specific "explosive" muscle power.
These and similar weight-lifting machines, however, have heretofore been expensive to make, difficult to operate, and carry a high potential for injury. In particular, the individual lifter must decide not only how much weight should go on the barbell but also how much supplemental load should be added, over what range the supplemental load should act, and how to configure the specific machine being used to establish these load levels and ranges. A mistaken choice by the lifter can result in the lifter being jerked downwardly underneath a load he can neither support nor manage and cause tearing of the lifter's muscles or injury to his back or chest region.
The severe injuries that have occurred with these or other types of weight-lifting devices have spurred the development of "self-spotting" devices. The purpose of these devices is to prevent the lifter from becoming pinned or crushed under a heavy weight and are designed to be activated by the lifter himself, during the exercise, without outside intervention. Existing self-spotting devices, however, do not adapt well to weight-lifting machines which develop sports-specific explosive muscle power.
In some machines, for example, travel of the barbell is artificially restricted along a linear path of travel adjacent a guide rail. This approach, for example, is shown in Dawson U.S. Pat. No. 4,564,194, where a barbell carrying hooklike pins is guided along two vertical struts which have a series of holes formed along their length. To stop the barbell during the exercise, the lifter rotates the bar so that the pins hook into the holes on the struts. This setup, however, would restrict natural muscle movement during exercises such as squats, where the bar is carried along a forward to rearward direction as well as along a vertical direction.
An alternative type of self-spotting device is shown in McCreery et al. U.S. Pat. No. 4,650,186. The MoCreery et al. device is intended to operate durinq a bench type exercise where the lifter lies face up on a bench and maneuvers the barbell, using his arms, in repetitive movements towards and away from his chest. The lifter operates the self-spotting device by pressing his feet against a foot pedal which raises a pair of support platforms that engage either side of the barbell. With the foot pedal, the lifter can use the combined power of his arms and legs to raise the bar onto a pair of upwardly mounted support hooks. This approach, however, would not permit explosive muscle development of the lifter's legs because the lifter must keep his legs free to activate the self-spotting device. Furthermore, if the lifter should collapse from strain after the foot pedal has been activated, the barbell can fall upon and crush the lifter.
Accordingly, it is an object of the present invention to provide a weight-lifting device for developing sports-specific "explosive" muscle power which is inexpensive to make and simple to operate.
A further object of the present invention is to provide a weight-lifting device having a self-spotting device which is compatible with free maneuverability of the weights by the lifter and which will protect the lifter against injury even if the lifter collapses from fatigue.